Variation of the lattice parameter with aluminum content in synthetic sodium faujasites. Evidence for ordering of the framework ions

Dempsey, E.; Kuehl, G. H.; Olson, David H.

doi:10.1021/j100722a020

Cited by 204 publications

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“…Dempsey, Kiihl, and Olson (25) suggested that the cell dimensions supported the concept of Si,Al order in the faujasite-type zeolites. Si02 and A1203.…”

Section: Aluminosilicate Frameworkmentioning

confidence: 76%

“…Thus, I disagree with the nomenclature proposed by Wright, Rupert, and Granquist (69,70), especially as their x-ray and infrared data indicate significant differences between the 2 types. Dempsey et al (25) restricted the use of the terms Y and X zeolite to the composition ranges 53-64 and 80-96 Al atoms per cell. The inter mediate range was denoted the Transition type ( Figure 3 ).…”

Section: Aluminosilicate Frameworkmentioning

confidence: 99%

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Faujasite-Type Structures: Aluminosilicate Framework: Positions of Cations and Molecules: Nomenclature

Smith

1974

Molecular Sieve Zeolites-I

105

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The framework distorts in response to cations and molecules. Type X zeolite has strong Al,Si long-range order, but the order-disorder in faujasite and Type Y zeolite is equivocal. Positions of framework hydroxyls in heated NH4-exchanged faujasite were inferred from interatomic distances and infrared data. Exchangeable cations in strictly dehydrated specimens occupy sites offering minimum electrostatic energy; the center of the hexagonal prism is preferred. For incomplete dehydration (typical for most commercial catalytic processes), cations bond to residual molecules in the sodalite units. The location of exchangeable cations and water molecules in hydrated specimens is uncertain. Hydration complexes of cations occur in the supercage. In the Al-rich varieties, cations certainly enter the sodalite unit. In the Al-poor varieties, x-ray diffraction evidence on cation positions is equivocal. / T 1 his paper reviews data available by January 1970 on the crystal A structures of materials containing an aluminosilicate framework with the topology of the mineral faujasite. The nomenclature will be discussed in more detail at the end. Briefly, names will be assigned which specify the treatment applied to the 3 basic starting materials-viz., faujasite, Linde Y, and Linde X zeolites. The latter 2 are synthetic materials prepared in hydrous sodium systems, the former being richer and the latter poorer in Si. The Si,Al content of Y overlaps that of faujasite.Although x-ray diffraction techniques can yield data on atomic positions and occupation frequency which appear highly precise, these data

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“…Dempsey, Kiihl, and Olson (25) suggested that the cell dimensions supported the concept of Si,Al order in the faujasite-type zeolites. Si02 and A1203.…”

Section: Aluminosilicate Frameworkmentioning

confidence: 76%

Section: Aluminosilicate Frameworkmentioning

confidence: 99%

Faujasite-Type Structures: Aluminosilicate Framework: Positions of Cations and Molecules: Nomenclature

Smith

1974

Molecular Sieve Zeolites-I

105

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“…The lattice parameter in three samples was determined using three peaks of (533), (822) and (555) ( Table 3). The determined lattice parameters (a) of 24.82-24.88Å were not categorized in X-type but in Y-type or the intermediate-type [33], suggesting that the synthesized FAU-type zeolite membranes were practically recognized to be NaY zeolite membrane. The accuracy of determined lattice parameters for FAU-type zeolite phase was assured to be within 1% by the comparison of simultaneous determination of lattice parameters of ␣-alumina (support phase) with those in JCPDS card no 83-2081 (Table 3).…”

Section: Synthesis Of Y-type Zeolite Membranesmentioning

confidence: 92%

Synthesis of industrial scale NaY zeolite membranes and ethanol permeating performance in pervaporation and vapor permeation up to 130°C and 570kPa

Sato¹,

Sugimoto²,

Nakane³

2008

Journal of Membrane Science

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“…Zeolites with a Si/Al ratio higher than 1 can be obtained from random substitution of aluminum by silicon, either ignoring [12,13] or taking into account distribution rules [14][15][16][17][18]. The aluminum atoms can also be assigned to energetic and entropic preferential positions [19][20][21][22][23][24], or using theoretical approaches that identifies experimentally accessible properties dependent on the aluminum distribution and associated cation distribution [25,26].…”

Section: Modeling Zeolites and Nonframework Cationsmentioning

confidence: 99%

Modeling of Transport and Accessibility in Zeolites

Calero¹

2010

Zeolites and Catalysis

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IntroductionModeling plays an important role in the field of zeolites and related porous materials. The use of molecular simulations allows the prediction of adsorption and diffusion coefficients in these materials and also provides important information about the processes taking place inside the porous structures at the molecular level [1-10]. Hence, molecular modeling is a very good complement to experimental work in the understanding of the molecular behavior inside the pores.Despite the great interest and the applicability of zeolites, there are still many facets of the molecular mechanisms for a given reaction inside their pores that are poorly understood. These mechanisms are important for (i) the way the zeolite adsorbs, diffuses, and concentrates the adsorbates near the specific active sites; (ii) the interactions between the zeolite and the adsorbates and the effect on the electronic properties of the system; (iii) the chemical conversion at the active site; and (iv) the way the zeolite disperses the final product. Detailed knowledge on the molecular mechanisms involved will eventually lead to an increase in the reaction efficiency.This chapter focuses on molecular modeling of transport and accessibility in zeolites. It describes how simulations have contributed to a better understanding of these materials and provides a summary of the state of the art as well as of current challenges. The chapter is organized as follows. First, common models and potentials are briefly described. This is followed by a general overview on current simulation methods to compute adsorption, diffusion, free energies, surface areas, and pore volumes. The chapter continues with some examples on applications of molecular modeling to processes of interest from the industrial and environmental point of view. Finally, the chapter closes with a summary and some remarks on future challenges.

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Variation of the lattice parameter with aluminum content in synthetic sodium faujasites. Evidence for ordering of the framework ions

Cited by 204 publications

References 0 publications

Faujasite-Type Structures: Aluminosilicate Framework: Positions of Cations and Molecules: Nomenclature

Faujasite-Type Structures: Aluminosilicate Framework: Positions of Cations and Molecules: Nomenclature

Synthesis of industrial scale NaY zeolite membranes and ethanol permeating performance in pervaporation and vapor permeation up to 130°C and 570kPa

Modeling of Transport and Accessibility in Zeolites

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